Display or capture media for images have been known for over 150 years. Today, these images are often organized into color planes, each plane representing the corresponding color components of the image. Black-and-white images have one plane, while color images generally have three, one each in a color primary, typically red, green, and blue. Images are often stored on negative or positive transparent film, color paper, or digitally on magnetic media. When stored digitally, uncompressed images are generally organized as sets of pixels, image lines, or image planes. Each element of the set represents a different color within the image. When stored on film, a separate physical layer of the film incorporates each color plane of the image. Traditional color silver halide paper uses a similar approach. Inkjet and thermal sublimation techniques deposit separate layers or pixels of primary colored inks.
False-color imaging systems are also well known. In these systems, invisible light (typically infrared or ultraviolet) exposes otherwise traditional imaging materials such as color film to produce a visible color in the exposed medium.
It is often useful to associate non-image information about an image with the image. Such information is often known as meta-data and comprises information such as time of image capture, location of capture, an image description, flash and exposure settings, audio clips, and so forth. This information can be used to optimize the display or use of the image itself. When images are stored digitally, associating such information with an image is straightforward. The meta-data is organized in some structured fashion and written as a header in the image file or otherwise associated with the image file.
Associating such information with images stored on hard-copy media is more problematic. Such a system is described in U.S. Pat. No. 5,763,891 issued Jun. 9, 1998 to Yoshinaga et al., entitled Non-Visualized Information Recording Medium and Apparatus for Detecting the Same.
Techniques are known for writing meta-data on a variety of hard-copy image media. For each of these techniques, invisible, light-responsive materials must be coated or otherwise applied to the medium, and methods to expose or otherwise write information in the invisible material, as well as read the information back, are known (e.g. see U.S. Pat. No. 5,995,193 issued Nov. 30, 1999 to Stephany et al., entitled Self-Contained Device for Recording Data Encoded Either in Visible or Invisible Form). Other materials, such as a thermal sublimation donor material coated with an additional, invisible layer capable of information storage on a receiver media, is known as is the use of an inkjet deposition system to provide an additional invisible layer for information storage on a paper inkjet print. U.S. Pat. No. 5,514,860 issued May 7, 1996 to Berson, entitled Document Authentication System Utilizing a Transparent Label describes placing a transparent tape over a medium. U.S. Pat. No. 5,841,885 issued Nov. 24, 1998 to Neff et al., entitled Print and Method and Apparatus for Printing, Storing and Retrieving an Image Record discloses storing additional digital information on the reverse of an image print.
There are also techniques known that utilize invisible magnetic layers to store information. For example, U.S. Pat. No. 5,229,259 issued Jul. 20, 1993 to Yokota, entitled Silver Halide Photographic Material discloses a silver halide photographic material with a magnetic recording layer. However, these systems and their associated meta-data associate information with the image as a whole and do not physically associate information with each image pixel on the recording medium.
In addition to meta-data describing attributes of an image, information related to each pixel can be useful, particularly if the hard-copy image media constrains the image information. Once written to the constrained medium, original image information is lost. For example, a residual image is the difference between one hard-copy representation of an image (typically color paper) and another less constrained representation (typically color film).
In general, it is possible to store any meta-data or additional information associated with the pixels of an image separately from the image pixels, either on the same hard-copy medium or in a separate location. In the latter case, the meta-data information may become disconnected from the image and lost. In the former case, the storage is inherently less robust in that if a portion of the image is lost or damaged, it is very likely that all of the information will be lost or unrecoverable. Moreover, there is a general problem with digital information storage in file formats. The formats tend to be very media or computer dependent and change rapidly. Hence, information stored in obsolete formats quickly becomes unrecoverable as the software and computer systems to support the format become unavailable.
As images become increasingly pervasive and the variety of image applications grows, additional pixel-related information beyond the traditional red, green, and blue (or cyan, yellow, magenta, and black) is becoming extremely useful. For example, applications such as image scene modeling, image differences, image understanding, multi-image scenes, and three-dimensional images, display require per-pixel information such as scene distance from capture device, pixel differences from other images, color/exposure attributes, or object classification information. This information can be captured or calculated in a variety of ways and readily stored in a digital system but robust storage and recovery of the additional information is problematic when associated with hard-copy film or paper media.
There is a need therefore for an improved method for storing and retrieving additional information associated with each pixel in an image on hard-copy media.